Application of brushless and non-loop starter in alumina plant Shangdong Kong Lingwei (China Aluminum Shandong Branch, Zibo 255051, Shandong, China) [Abstract] This paper briefly describes the current status of wound induction motors, brushless and ringless variable resistance starting. Product structure characteristics, working principles, and the promotion and use of the alumina plant. [Key words] starter; brushless starter; electromagnetic components; varistor; rotor circuit; steady speed [China Classification] TF821 [Document Identification Code] B [Article ID] 1008-5122 (2004) 04-0003-03 1 Summary Three-phase wound asynchronous motor is one of the main dragging equipments of alumina plant. Because it can have external resistance or reactance on the rotor, it has higher power factor and higher starting torque and energy at startup. The advantages of changing the operating speed, etc., are widely used as drag devices in ball mills, clinker kilns, blowers, vacuum pumps and other equipment. However, the wound-type asynchronous motor must be connected with a resistor or a reactor in the rotor circuit of the motor to increase the starting torque of the motor and reduce the starting current. During the start-up process, the value of this resistance or reactance also changes gradually from large to small, until the next zero, the motor start process is completed, enter the running state, to use a complex auxiliary starting device to complete the motor Boot process. Its starting auxiliary equipment is relatively complex, mainly including slip rings for access resistors, brushes, metal resistors with segmented cut-out (or frequency-sensitive resistors with relatively smooth characteristic curves), short-circuiting short-circuiting devices for short-circuiting rotor circuits, and AC Contactor. The installation and commissioning of this device are complex, and the operation is troublesome. The accident rate is high, the maintenance is difficult, the spare parts are consumed in large quantities, and the maintenance cost is high. Due to the segmented cut-off resistance, the starting characteristic curve of the motor is formed into a stepped shape, which cannot be smoothly started and continuously variable, and the characteristics are poor and the energy consumption is large. Frequently-used frequency-sensitive rheostats overcome the characteristic of the step-like characteristic curve generated by the segmented cut-off resistors, achieving linear changes in resistance during motor start-up, stepless speed changes, and smooth and reliable characteristic curves. However, it only solves the problem of the start-up characteristics of the motor and does not solve the complicated starting aid for the motor. The brushless and loopless starter not only solves the problem of poor starting characteristics of the metal resistor and the reactor, but also solves the complicated problem of the commonly used frequency sensitive resistance starting aid, and composes the complicated starting aid of the original secondary circuit system of the wound motor. A non-contact electromagnetic element is directly mounted on the rotor shaft of the motor, which solves a major problem of the starting device of the winding motor and shows a strong vitality. 2. Principle of operation The brushless and loopless starter is a new type of linear variable resistance starter developed using the principle of frequency sensitive varistor. It is the multi-contact element of the original secondary circuit system and consists of a non-contact electromagnetic element, equivalent to one, etc. The value impedance is in series with the rotor of the wound rotor. As a starting device for the varistor at startup, the major difference between it and the conventional frequency sensitive varistor is that it still participates in motor dragging after assisting the motor in completing the variable resistance start task. Moving the whole process, and the traditional frequency sensitive rheostat can not participate in the motor dragging operation. If the frequency sensitive rheostat is not removed in time, it will cause the rheostat to overheat and even burn out. The asynchronous motor can't be operated at normal speed, and the current is increased. , it will even burn the motor. The brushless and acyclic starter adopts the principle of a better magnetic circuit. It consists of a coil winding, an inner and outer iron core, a bushing, a yoke plate, and a terminal column to form a contactless electromagnetic element. It is installed in the slip ring position on the original motor rotor. Its unique structural features allow the brushless starter to have a large impedance value at the start of startup, while the impedance value is almost zero in the operating state. During the whole start-up process, the impedance value changes linearly, the curve is smooth, and the start of the motor is infinitely variable, stable and reliable, and the starting torque is large and the starting current is small. When the stator winding of the motor is just connected to the power supply, the voltage frequency of the rotor winding is 50Hz. Acting on the coil of the starter becomes a load with a larger impedance and is brought into the rotor circuit. Therefore, the current in the rotor circuit becomes smaller, and The current value in the corresponding stator circuit also becomes smaller. As the rotation speed changes from slow to fast, the frequency of the rotor circuit induced voltage also changes from high to low. When the rotor reaches the rated speed, the induction frequency of the rotor circuit also approaches zero. The impedance of the starter is also close to zero, completing the start-up task of the wound motor. At this time, the starter still participates in the operation of the motor. Because the impedance value of the starter is close to zero at this time, it is equivalent to the operating state of the carbon brush slip ring. Therefore, the brushless and loopless starter will not affect the normal operation of the motor. It is an ideal starting device. 3. Application example 3.1 Application of brushless and non-loop starter on vacuum pump In April of 1999, the No. 3 vacuum pump motor of the No. 4 workshop was first transformed. The vacuum pump motor is a JR127-6 185kW motor produced by the Guangzhou Electric Machinery Factory. It uses two. The secondary loop series frequency sensitive resistors are activated by a brush short circuit mechanism and an AC contactor with a shorted rotor circuit. The operation is very inconvenient, often due to short circuit start to burn the short circuit contact and the motor rotor coil, sometimes because the short circuit mechanism is not flexible to burn out the short circuit contact point, the motor slip ring and the carbon brush often malfunction. Spare parts consume a large amount, high maintenance costs, can not meet the production requirements. After the transformation, the starter auxiliary device, frequency-sensitive rheostat, and secondary circuit of the winding motor were removed, the operation was simple, the operator did not have to worry about the short-circuit start, and the overhaul was very convenient. The operation did not occur for more than six months. One failure, simple operation, smooth operation, and favored by operating workers, see Table 1 before and after the transformation. Table 1 Comparison of vacuum pump motor before and after the technical data comparison Starting power at the start of electrical operation Electrical working temperature (A) (S) Factor flow (A) Degree (°C) Effect (yuan) Before the transformation 560 12 0.86 220 55 After the transformation 540 8 0.87 210 40 20148 Note: The price of electricity is 0.46 yuan/kWh. From the comparison table of technical data before and after the transformation, it can be seen that the starting current of the motor after the transformation is reduced, the starting performance is changed, and the running current is decreased, and the power factor is increased. In the case of an ambient temperature of 30°C, the starter's operating temperature is less than 40°C and good start-up performance. It is an ideal starting element. 3.2 Application of brushless and non-loop starter on ball mill On the basis of the successful transformation of more than a dozen vacuum pumps in the whole plant, we have modified the No. 2 wet grinding in No.4 workshop. 2# Wet grinding is a ball mill. It is equipped with a motor JR128-8 155kW wound asynchronous motor and starts with a frequency sensitive rheostat. As the ball mill is stopped, the steel ball accumulates at the bottom of the grinding wheel, and a lot of material remains at the bottom of the grinding wheel. It is very difficult to start, and sometimes a series of metal resistors have to be connected in series on the basis of the original frequency sensitive resistance to change the starting characteristics of the motor. After the brushless and ringless starter is used, the starting performance of the motor is greatly improved, the starting torque is greatly increased, the starting current is reduced, and the starting time is short. This fully meets the motor start-up requirements, solves the long-term problems that plagued us, and reduces a lot of Maintenance time laid the foundation for the renovation of other ball mills. Due to changes in the feed amount of the ball mill and changes in the production process conditions, the motor will be overloaded to increase the current, and the overcurrent action will cause the motor to stop operating. Due to the large load current, the motor's slip ring carbon brush will generate heat, stab fire, and even burn red carbon brush, burn the slip ring, and even burn the motor rotor coil. After the brushless and ringless starter is used, when the motor decelerates due to overload, the inductive frequency of the rotor circuit increases with decreasing speed, and the impedance of the starter increases accordingly, thereby increasing the drag torque of the motor. It also reduces the motor current and avoids the ball mill tripping due to overcurrent. In actual operation, when the load changes, after the motor current fluctuates, the rotation speed of the motor can quickly return to normal, and the rotation speed of the motor basically remains unchanged. Therefore, the brushless and non-loop starter has a steady speed function. 3.3 Application of brushless and ringless starter on high-voltage motor The pulverized coal grinding motor is a high-voltage motor for grinding pulverized coal. The motor is a JR157-8 320kW wound-rotor asynchronous motor, rated voltage is 6KV, rotor voltage is 501V, rotor current For 391A, start with a frequency-sensitive rheostat. The pulverized coal workshop requires a high level of fire protection, and the start-up device of the winding-type asynchronous motor is complex and there are potential safety hazards. The pulverized coal mill belongs to a ball mill and has all the characteristics of a ball mill. Because the dry pulverized coal is pulverized, the load is relatively low in wet milling. Therefore, on the basis of the successful reconstruction of the wet pulverizing motor, the pulverized coal pulverizing motor was brushless-free. The transformation of the ring was very successful after the transformation and the effect was obvious. The comparison before and after the transformation is shown in Table 2. Table 2 Comparison of technical data before and after transformation of high-voltage motors Power operation during start-up Electric operation Operating temperature Period current (A) (S) Factor flow (A) Degree (°C) Effect (yuan) Before the transformation 82 15 0.85 36 43 After transformation 80 13 0.86 35.2 38 44326 Note: Electricity price 0.46 yuan/kWh 4. Several problems in the application process (1) Brushless and non-ring starter should use products made by professional manufacturers, otherwise it will cause difficulties in starting. (2) The ball mill should be fully considered with respect to the load and a reasonable overload factor should be selected. (3) Low system voltage is one of the main reasons for the difficulty in starting a brushless and loopless starter. (4) Brushless and ringless starters cannot participate in speed regulation and cannot be applied to speed control equipment. 5. Concluding remarks The application of the brushless and loopless starter removes the complex starting systems such as the slip ring, carbon brush, brush box, and secondary circuit of the short circuit ring. Not only can it be started directly, but it also maintains the excellent performance of the wound motor. It has a steady speed function when the load is overloaded. It is an easy-to-operate, maintenance-free, operation-free, energy-efficient winding motor starter. The application of brushless and acyclic starters greatly simplifies the operating procedures of operators and saves a large amount of maintenance costs each year. Each brushless and acyclic starter saves spare parts annually (slip ring, carbon brush, brush box and short-circuit ring , AC contactors, relays) worth about 8,000 yuan, saving about 20000-50000 yuan, it is worth promoting in the whole plant. The brushless starter is involved in the whole process of starting and running the motor. It does not participate in the speed regulation of the motor and is not suitable for equipment that needs speed regulation. However, it still has a broad prospect for development in the production of alumina. At present, all alumina plant vacuum pump motors, four workshop ball mill motor, pulverized coal motor (high pressure), pulverized coal bridge hoist winch motor, cart motor, 8 # rotary kiln exhaust fan motor (high pressure) have all been applied Brush starter, energy-saving effect is more obvious. -----From "non-ferrous metallurgical energy-saving" August 2004, No. 4 The manufacturer of brushless acyclic starters in this article is: Chengdu Jinnengda Starter Manufacturing Co., Ltd. (formerly Chengdu Shida Electronic Instrument Factory) Address : Chengdu City Jiuyan Bridge 720 Research Institute of Sichuan University Postcode: 610064 Telephone: 028-85412731 Fax: 028-85471609 Contact person: Liu Caixia http:// E-mail: Chengdu Jinnengda Starter Manufacturing Co., Ltd. was developed in 1988 China's brushless and acyclic starter on the foreground, WSBQ series brushless acyclic starter is widely used in metallurgy, cement, chemical and other industrial and mining enterprises start the motor. The product has the following advantages: 1. Simple structure: Eliminate all electrical components such as slip ring, carbon brush and secondary circuit. 2. Steady start: Continuously variable speed, stable and reliable, large starting torque and small starting current. 3, reliable operation: to achieve brushless and loopless operation of AC winding motor, to prevent the occurrence of operational accidents. 4, exempt from maintenance: no maintenance, spare parts costs. 5, overload steady speed: When the motor load overload, the starter has a steady speed function. 6. Improve the operating rate: The motor runs more reliably, greatly increasing the operating rate of the equipment. 7, the product is economic and durable, the warranty period of more than five years.